A Jesuit missionary of the eighteenth century noted for his exploration of the Amazon River and its basin; b. at Trautenau, Bohemia, in 1654; d. 20 March, 1728. He joined the Society of Jesus in 1673. In 1684 he was sent to Quito as a missionary. For forty-two years Fritz acted in this capacity among the Indians of the Upper Marañon. He succeeded in converting among others the powerful tribe of Omaguas (Omayas) and in concentrating into civilized settlements the savages of forty different localities, in the country between the Rivers Napo and Negro. An adept in technical arts and handicraft, he also was extraordinary linguistic abilities, supplemented by the rare gift of knowing intuitively how to treat the Indians. These qualifications enabled him to accomplish prodigious work among them, and merited for him the respect not only of the savages but also of the Spanish Government, to which he rendered valuable service in its boundary dispute with the Portuguese. At the instance of the Real Audiencia of Quito he began (1687) the cartographical delineation of the disputed missionary territory on the Upper Marañon between Peru and Quito. In 1689 he undertook, in a primitive pirogue, a daring expedition down the Amazon to Pará, where he was captured and imprisoned for two years on the suspicion of being a Spanish spy. Although imperfectly equipped with the necessary instruments, he completed a comparatively accurate chart of the river's course. This was the first approximately correct chart of the Marañon territory. He was also the first to follow the Tunguragua instead of the Gran Pará (Ucayali) and prove it the real source of the Marañon.

A Protestant, Wappaeus, writes of him in his "Handbuch der Geographie und Statistik" (Leipzig, 1863-70, I, pt. III, 595) as follows: "The great respect justly shown at that time by European scientists for the geographical work of the Jesuits led to the admission into their ranks of Father Fritz by acclamation." In 1707 this map was printed at Quito and extensively copied, e.g. in the "Lettres Edifiantes" (Paris, 1781), VIII, 284, and the "N. Welt-Bott" (Augsburg, 1726, I), also in Condamine, "Relation abrégée d'un voyage fait dans l'intérieur de l'Amérique Mérid." (Paris, 1745), which contains the revised chart of Father Fritz for comparative study. The chart was reprinted in Madrid, in 1892, on the occasion of the fourth centenary of the discovery of America. There was another reprint in the "Recueil de voyage et de documents pour servir a l'hist. de la géogr.", ed. by Schéfer and Cordier (Paris, 1893). Three of his letters are incorporated in the "N. Welt-Bott" (Augsburg, 1726), III, nos. 24, 25; according to Condamine an original report of his travels is to be found in the archives of the Jesuit college at Quito.